CN111697267A - Electrolyte solution, electrochemical device containing electrolyte solution, and electronic device - Google Patents

Electrolyte solution, electrochemical device containing electrolyte solution, and electronic device Download PDF

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CN111697267A
CN111697267A CN202010587893.XA CN202010587893A CN111697267A CN 111697267 A CN111697267 A CN 111697267A CN 202010587893 A CN202010587893 A CN 202010587893A CN 111697267 A CN111697267 A CN 111697267A
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substituted
electrolyte
unsubstituted
compound
fluorine atom
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管明明
熊亚丽
郑建明
崔辉
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Ningde Amperex Technology Ltd
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Ningde Amperex Technology Ltd
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0566—Liquid materials
    • H01M10/0567—Liquid materials characterised by the additives
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Abstract

The present application relates to an electrolyte including a thiane compound and a polynitrile compound, and an electrochemical device and an electronic device including the same. The electrochemical device of the present application, including the electrolyte, has significantly improved cycle performance and high and low temperature storage performance.

Description

Electrolyte solution, electrochemical device containing electrolyte solution, and electronic device
Technical Field
The present disclosure relates to the field of energy storage technologies, and more particularly, to an electrolyte, and an electrochemical device and an electronic device including the electrolyte.
Background
Lithium ion batteries are currently the most promising energy storage form due to their long service life, high energy density, low environmental pollution, etc., and therefore are widely used in the fields of intelligent products (including electronic products such as mobile phones, notebooks, cameras, etc.), electric tools, electric vehicles, etc., and are gradually replacing conventional nickel-cadmium batteries, nickel-hydrogen batteries, and lead-acid batteries. However, as the energy consumption of the terminal products increases and the usage scenarios diversify, the cycle life of the lithium ion battery becomes a pain point for users to use, and therefore, the development of the lithium ion battery with a long service life becomes a problem which needs to be solved urgently at present.
In order to improve the cycle performance of the lithium ion battery, a common strategy is to add positive and negative film-forming additives into the electrolyte, and the positive and negative film-forming additives can significantly deteriorate the impedance of the lithium ion battery, so that the cycle performance cannot be improved while the low-temperature performance of the lithium ion battery cannot be considered. In order to improve the low-temperature performance of the lithium ion battery, a common method is to improve the dynamics of the electrolyte, but the high-dynamics electrolyte often seriously deteriorates the high-temperature cycle performance and the high-temperature storage performance of the lithium ion battery. Therefore, it is necessary to develop an electrolyte that can simultaneously achieve both the cycle life and the high and low temperature performance of the lithium ion battery.
Disclosure of Invention
The present application provides an electrolyte and an electrochemical device including the electrolyte, in an attempt to solve at least one of the problems existing in the related art to at least some extent.
The application provides an electrolyte containing a thiane compound and a polynitrile compound, which can form a low-impedance protective film on a positive electrode interface and a negative electrode interface, thereby improving the high-low temperature performance of an electrochemical device and improving the cycle performance of the electrochemical device.
According to an embodiment of the present application, there is provided an electrolyte including a thiane compound and a polynitrile compound represented by formula I
Figure BDA0002555335640000021
Wherein R is1、R2、R3、R4Each independently selected from substituted or unsubstituted C1To C6Alkylene or sulfonyl, wherein, when substituted, the substituent is cyano, sulfonylmethyl, C1To C6At least one of an alkoxy group or a fluorine atom.
According to embodiments herein, the thiane compound comprises:
Figure BDA0002555335640000022
Figure BDA0002555335640000023
at least one of (1).
According to embodiments herein, the weight percentage of the thianes is 0.05 wt% to 10 wt% based on the weight of the electrolyte; the polynitrile compound is 0.1 wt% to 10 wt%.
According to embodiments of the present application, the polynitrile compound comprises a compound of formula II
Figure BDA0002555335640000024
Wherein R is6Is cyano, fluorine atom, hydrogen atom, substituted or unsubstituted C1To C6Alkyl or substituted or unsubstituted C1To C6Alkoxy, wherein when substituted, the substituent is at least one of cyano, fluorine atom or sulfone group; wherein R is5、R7Each independently selected from substituted or unsubstituted C1To C6Alkylene or substituted or unsubstituted C1To C6And an alkyleneoxy group, wherein when substituted, the substituent is at least one of a cyano group, a fluorine atom, or a sulfone group.
According to embodiments of the present application, the polynitrile compound comprises:
Figure BDA0002555335640000025
Figure BDA0002555335640000031
Figure BDA0002555335640000032
at least one of (1).
According to an embodiment of the present application, the electrolyte further comprises a cyclic sulfate compound represented by formula III
Figure BDA0002555335640000033
Wherein R is9、R11Each independently selected from substituted or unsubstituted C1To C6Alkylidene, wherein when substituted, the substituent is cyano, sulfonyl methylRadical, fluorosulfonyl radical, C1To C6At least one of an alkoxy group or a fluorine atom; wherein R is10Selected from oxygen atoms, substituted or unsubstituted C1To C6Alkylene, wherein, when substituted, the substituents are cyano, sulfonylmethyl, fluorosulfonyl, C1To C6At least one of an alkoxy group or a fluorine atom; wherein R is8、R12Each independently selected from a hydrogen atom, a fluorine atom, a substituted or unsubstituted C1To C6Alkyl, wherein when substituted, the substituent is sulfonylmethyl, fluorosulfonyl or C1To C6At least one of an alkoxy group, a fluorine atom, or a cyano group.
According to an embodiment of the application, wherein the weight percentage of the cyclic sulfate compound is 0.1 to 10 wt% based on the weight of the electrolyte.
According to embodiments of the application, the cyclic sulfate compound comprises:
Figure BDA0002555335640000041
at least one of (1).
According to embodiments herein, the electrolyte further comprises a carbonate additive comprising at least one of a compound of formula IV-a, a compound of formula IV-B, or a compound of formula IV-C:
Figure BDA0002555335640000043
wherein R is13、R14Each independently selected from a hydrogen atom, a fluorine atom, a cyano group, a substituted or unsubstituted C1To C6Alkyl, substituted or unsubstituted C2To C6Alkenyl, substituted or unsubstituted C2To C6Alkynyl, substituted or unsubstituted C6To C10Aryl or substituted or unsubstituted-Rb-O-RaWherein R isaIs cyano or C1To C3Alkyl radical, RbIs a single bond or C1To C3Wherein is takenWhen substituted, the substituent is at least one of cyano, sulfuryl or fluorine atom; wherein R is15、R16、R17、R18Each independently selected from a hydrogen atom, a fluorine atom, a cyano group, a substituted or unsubstituted C1To C6Alkyl, substituted or unsubstituted C2To C6Alkenyl, substituted or unsubstituted C2To C6Alkynyl, substituted or unsubstituted C6To C10Aryl or substituted or unsubstituted C1To C6Alkoxy, wherein when substituted, the substituent is at least one of cyano, sulfone or fluorine atom; and R is13、R14Not simultaneously being a hydrogen atom, R17、R18At least one of which is substituted with a fluorine atom.
According to embodiments herein, the weight percentage of the carbonate additive is 0.1 wt% to 20 wt% based on the weight of the electrolyte.
According to embodiments herein, the carbonate additive comprises:
Figure BDA0002555335640000051
at least one of (1).
According to an embodiment of the present application, there is provided an electrochemical device including a positive electrode, a negative electrode, a separator, and any one of the above-described electrolytic solutions.
According to an embodiment of the present application, the anode includes an anode active material, and the Dv50 of the anode active material particles is 10 μm to 18 μm.
According to an embodiment of the present application, there is provided an electronic device including any one of the electrochemical devices described above.
Additional aspects and advantages of embodiments of the present application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of embodiments of the present application.
Detailed Description
Embodiments of the present application will be described in detail below. The embodiments described herein are illustrative and are provided to provide a basic understanding of the present application. The embodiments of the present application should not be construed as limiting the present application.
As used herein, the terms "substantially", "substantially" and "about" are used to describe and illustrate minor variations. When used in conjunction with an event or circumstance, the terms can refer to instances where the event or circumstance occurs precisely as well as instances where the event or circumstance occurs in close proximity. For example, when used in conjunction with numerical values, the term can refer to a range of variation that is less than or equal to ± 10% of the stated numerical value, such as less than or equal to ± 5%, less than or equal to ± 4%, less than or equal to ± 3%, less than or equal to ± 2%, less than or equal to ± 1%, less than or equal to ± 0.5%, less than or equal to ± 0.1%, or less than or equal to ± 0.05%. For example, two numerical values are considered to be "substantially" identical if the difference between the two numerical values is less than or equal to ± 10% (e.g., less than or equal to ± 5%, less than or equal to ± 4%, less than or equal to ± 3%, less than or equal to ± 2%, less than or equal to ± 1%, less than or equal to ± 0.5%, less than or equal to ± 0.1%, or less than or equal to ± 0.05%) of the mean of the values.
Additionally, amounts, ratios, and other numerical values are sometimes presented herein in a range format. It is to be understood that such range format is used for convenience and brevity, and should be interpreted flexibly to include not only the numerical values explicitly recited as the limits of the range, but also to include all the individual numerical values or sub-ranges encompassed within that range as if each numerical value and sub-range is explicitly recited.
In the detailed description and claims, a list of items linked by the term "at least one of," "at least one of," or other similar terms may mean any combination of the listed items. For example, if items a and B are listed, the phrase "at least one of a and B" means a only; only B; or A and B. In another example, if items A, B and C are listed, the phrase "at least one of A, B and C" means a only; or only B; only C; a and B (excluding C); a and C (excluding B); b and C (excluding A); or A, B and C. Item A may comprise a single component or multiple components. Item B may comprise a single component or multiple components. Item C may comprise a single component or multiple components.
The term "alkyl" is intended to be a straight chain saturated hydrocarbon structure having from 1 to 20 carbon atoms. "alkyl" is also contemplated to be a branched or cyclic hydrocarbon structure having from 3 to 20 carbon atoms. For example, the alkyl group may be an alkyl group of 1 to 20 carbon atoms, an alkyl group of 1 to 10 carbon atoms, an alkyl group of 1 to 5 carbon atoms, an alkyl group of 5 to 20 carbon atoms, an alkyl group of 5 to 15 carbon atoms, or an alkyl group of 5 to 10 carbon atoms. When an alkyl group having a particular carbon number is specified, all geometric isomers having that carbon number are intended to be encompassed; thus, for example, "butyl" is meant to include n-butyl, sec-butyl, isobutyl, tert-butyl, and cyclobutyl; "propyl" includes n-propyl, isopropyl and cyclopropyl. Examples of alkyl groups include, but are not limited to, methyl, ethyl, n-propyl, isopropyl, cyclopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, cyclobutyl, n-pentyl, isopentyl, neopentyl, cyclopentyl, methylcyclopentyl, ethylcyclopentyl, n-hexyl, isohexyl, cyclohexyl, n-heptyl, octyl, cyclopropyl, cyclobutyl, norbornyl, and the like. In addition, the alkyl group may be optionally substituted.
The term "alkylene" alone or as part of another substituent means a divalent radical derived from an alkyl group.
The term "alkylidene" alone or as part of another substituent means a trivalent radical derived from an alkyl group.
The term "alkoxy" refers to a L-O-group, wherein L is alkyl. The alkoxy group herein may be an alkoxy group of 1 to 12 carbon atoms, and may also be an alkoxy group of 1 to 10 carbon atoms, an alkoxy group of 1 to 5 carbon atoms, an alkoxy group of 5 to 12 carbon atoms, or an alkoxy group of 5 to 10 carbon atoms.
The term "alkyleneoxy" alone or as part of another substituent means a divalent radical derived from an alkoxy group.
The term "alkenyl" refers to a monovalent unsaturated hydrocarbon group that can be straight or branched chain and has at least one and typically 1, 2, or 3 carbon-carbon double bonds. Unless otherwise defined, the alkenyl group typically contains 2 to 20 carbon atoms, and may be, for example, an alkenyl group of 2 to 20 carbon atoms, an alkenyl group of 6 to 20 carbon atoms, an alkenyl group of 2 to 10 carbon atoms, or an alkenyl group of 2 to 6 carbon atoms. Representative alkenyl groups include, by way of example, ethenyl, n-propenyl, isopropenyl, n-but-2-enyl, but-3-enyl, n-hex-3-enyl, and the like. In addition, the alkenyl group may be optionally substituted.
The term "alkynyl" refers to a monovalent unsaturated hydrocarbon group that can be straight-chain or branched and has at least one, and typically 1, 2, or 3 carbon-carbon triple bonds. Unless otherwise defined, the alkynyl group typically contains 2 to 20 carbon atoms, and may be, for example, an alkynyl group of 2 to 20 carbon atoms, an alkynyl group of 6 to 20 carbon atoms, an alkynyl group of 2 to 10 carbon atoms, or an alkynyl group of 2 to 6 carbon atoms. Representative alkynyl groups include, for example, ethynyl, prop-2-ynyl (n-propynyl), n-but-2-ynyl, n-hex-3-ynyl, and the like. In addition, the alkynyl group may be optionally substituted.
The term "aryl" encompasses monocyclic and polycyclic ring systems. Polycyclic rings can have two or more rings in which two carbons are common to two adjoining rings (the rings are "fused"), wherein at least one of the rings is aromatic, e.g., the other rings can be cycloalkyls, cycloalkenyls, aryls, heterocyclics, and/or heteroaryls. For example, the aryl group may be C6To C50Aryl radical, C6To C40Aryl radical, C6To C30Aryl radical, C6To C20Aryl or C6To C10And (4) an aryl group. Representative aryl groups include, for example, phenyl, methylphenyl, propylphenyl, isopropylphenyl, benzyl, and naphthalen-1-yl, naphthalen-2-yl, and the like. In addition, the aryl group may be optionally substituted.
As used herein, the term "halogen" may be F, Cl, Br or I.
When the above substituents are substituted, the substituents may be selected from the group consisting of: halogen, alkyl, cycloalkyl, alkenyl, aryl and heteroaryl.
Embodiments of the present application provide an electrolyte and an electrochemical device and an electronic device including the same. In some embodiments, the electrochemical device is a lithium ion battery.
First, electrolyte
Embodiments of the present application provide an electrolyte comprising an organic solvent, an electrolyte, and an additive comprising a thiane compound and a polynitrile compound. In some embodiments, the electrolyte is a nonaqueous electrolyte.
The thiane compound and the polynitrile compound act together in the electrolyte, and an interfacial film formed on the negative electrode has good ionic conductivity and low impedance; meanwhile, the positive electrode can be stabilized, the dissolution of transition metal of the positive electrode is inhibited, the interface stability of the positive electrode is enhanced, and the impedance, the low capacity retention rate and the high temperature cycle performance of the electrochemical device can be obviously improved.
Thiane compounds
In some embodiments, the thiane compounds comprise compounds of formula I
Figure BDA0002555335640000081
In the formula I, R1、R2、R3、R4Each independently selected from substituted or unsubstituted C1To C6Alkylene or sulfonyl, wherein, when substituted, the substituent is cyano, sulfonylmethyl, C1To C6At least one of an alkoxy group or a fluorine atom.
In some embodiments, the thiane compound comprises:
Figure BDA0002555335640000082
Figure BDA0002555335640000083
at least one of (1).
In some embodiments, the weight percent of the thiane compound is 0.05 wt% to 10 wt% based on the weight of the electrolyte. In some embodiments, the weight percent of the thiane compound is about 0.05 wt%, about 0.1 wt%, about 0.5 wt%, about 0.8 wt%, about 1 wt%, about 2 wt%, about 3 wt%, about 4 wt%, about 5 wt%, about 6 wt%, about 7 wt%, about 8 wt%, about 9 wt%, about 10 wt%, 0.1 wt% to 5 wt%, 1 wt% to 3 wt%, 1 wt% to 5 wt%, 1 wt% to 10 wt%, or 5 wt% to 10 wt%, etc., based on the weight of the electrolyte.
Polynitrile compounds
In some embodiments, the polynitrile compound comprises a compound of formula II
Figure BDA0002555335640000084
In formula II, R6Is cyano, fluorine atom, hydrogen atom, substituted or unsubstituted C1To C6Alkyl or substituted or unsubstituted C1To C6Alkoxy, wherein when substituted, the substituent is at least one of cyano, fluorine atom or sulfone group; r5、R7Each independently selected from substituted or unsubstituted C1To C6Alkylene or substituted or unsubstituted C1To C6And an alkyleneoxy group, wherein when substituted, the substituent is at least one of a cyano group, a fluorine atom, or a sulfone group.
In some embodiments, the polynitrile compound comprises:
Figure BDA0002555335640000091
Figure BDA0002555335640000092
at least one of (1).
In some embodiments, the weight percent of the polynitrile compound is from 0.1 wt% to 10 wt% based on the weight of the electrolyte. In some embodiments, the weight percent of the polynitrile compound is about 0.1, about 0.5, about 1, about 2, about 3, about 4, about 5, about 6, about 7, about 8, about 9, about 10, 0.1 to 5, 1 to 3, 1 to 5, 3 to 5, or 5 to 10 weight percent, etc., based on the weight of the electrolyte.
In some embodiments, the weight percent of the thiane compound is a% and the weight percent of the polynitrile compound is b%, based on the weight of the electrolyte, satisfying 1. ltoreq. a + b. ltoreq.12. In some embodiments, the weight percent of the thiane compound is a% and the weight percent of the polynitrile compound is b%, based on the weight of the electrolyte, satisfying 1. ltoreq. a + b. ltoreq.10. In some embodiments, the weight percent of the thiane compound is a% and the weight percent of the polynitrile compound is b%, based on the weight of the electrolyte, satisfying 1. ltoreq. a + b. ltoreq.8. The content of the thiane compound and the polynitrile compound is in the range, so that an interfacial film formed by the negative electrode has better ion conductivity; meanwhile, the dissolution of the transition metal of the positive electrode can be better inhibited, and the impedance, the low-temperature cycle performance and the high-temperature cycle performance of the electrochemical device can be more remarkably improved.
In some embodiments, the weight percent of the thiane compound is a% and the weight percent of the polynitrile compound is b%, based on the weight of the electrolyte, and satisfies 0.1. ltoreq. a/b. ltoreq.15. The content of the thiane compound and the polynitrile compound is in the range, so that an interfacial film formed by the negative electrode has better ion conductivity; meanwhile, the dissolution of the transition metal of the positive electrode can be better inhibited, and the impedance, the low-temperature cycle performance and the high-temperature cycle performance of the electrochemical device can be more remarkably improved.
Cyclic sulfate compound
In some embodiments, the electrolytes of the present application can also include a cyclic sulfate compound of formula III
Figure BDA0002555335640000101
In formula III, R9、R11Each independently selected from substituted or unsubstituted C1To C6Alkylidene, wherein when substituted, the substituent is cyano, sulfonylmethyl, fluorosulfonyl, C1To C6At least one of an alkoxy group or a fluorine atom; r10Selected from oxygen atoms, substituted or unsubstituted C1To C6Alkylene, wherein, when substituted, the substituentIs cyano, sulfonylmethyl, fluorosulfonyl, C1To C6At least one of an alkoxy group or a fluorine atom; r8、R12Each independently selected from a hydrogen atom, a fluorine atom, a substituted or unsubstituted C1To C6Alkyl, wherein when substituted, the substituent is sulfonylmethyl, fluorosulfonyl or C1To C6At least one of an alkoxy group, a fluorine atom, or a cyano group.
In some embodiments, the cyclic sulfate compound comprises:
Figure BDA0002555335640000102
Figure BDA0002555335640000111
at least one of (1).
The cyclic sulfate compound can act synergistically with a thiophene compound and a polynitrile compound to form an organic-inorganic composite film on a negative electrode, and the composite film has good mechanical strength and can remarkably improve the side reaction of a negative electrode interface in a circulation process; the composite membrane also has good electrochemical stability and thermal stability, further optimizes ion conduction in the interfacial membrane, and obviously improves the low-temperature discharge performance of the battery.
In some embodiments, the weight percentage of the cyclic sulfate compound is 0.1 wt% to 10 wt% based on the weight of the electrolyte. In some embodiments, the weight percentage of the cyclic sulfate compound is about 0.1 wt%, about 0.5 wt%, about 1 wt%, about 1.5 wt%, about 2 wt%, about 2.5 wt%, about 3 wt%, about 3.5 wt%, about 4 wt%, about 4.5 wt%, about 5 wt%, about 5.5 wt%, about 6 wt%, about 6.5 wt%, about 7 wt%, about 7.5 wt%, about 8 wt%, about 8.5 wt%, about 9 wt%, about 9.5 wt%, 10 wt%, 0.1 wt% to 5 wt%, 1 wt% to 3.5 wt%, 1 wt% to 5 wt%, or 5 wt% to 10 wt%, etc., based on the weight of the electrolyte.
Carbonate additives
In some embodiments, the electrolytes of the present application can further comprise a carbonate additive comprising at least one of formula IV-A, formula IV-B, or formula IV-C:
Figure BDA0002555335640000113
in the formula IV-A, R13、R14Each independently selected from a hydrogen atom, a fluorine atom, a cyano group, a substituted or unsubstituted C1To C6Alkyl, substituted or unsubstituted C2To C6Alkenyl, substituted or unsubstituted C2To C6Alkynyl, substituted or unsubstituted C6To C10Aryl or substituted or unsubstituted-Rb-O-RaWherein R isaIs cyano or C1To C3Alkyl radical, RbIs a single bond or C1To C3Wherein when substituted, the substituent is at least one of a cyano group, a sulfone group or a fluorine atom. In the formulae IV-B and IV-C, R15、R16、R17、R18Each independently selected from a hydrogen atom, a fluorine atom, a cyano group, a substituted or unsubstituted C1To C6Alkyl, substituted or unsubstituted C2To C6Alkenyl, substituted or unsubstituted C2To C6Alkynyl, substituted or unsubstituted C6To C10Aryl or substituted or unsubstituted C1To C6Alkoxy, wherein when substituted, the substituent is at least one of cyano, sulfone or fluorine atom; and R is13、R14Not being hydrogen atoms at the same time; r17、R18At least one of which is substituted with a fluorine atom.
In some embodiments, the carbonate additive comprises:
Figure BDA0002555335640000121
at least one of (1).
The carbonate additive, the thiophene compound and the polynitrile compound act together, so that the transference number of lithium ions can be increased, the composition of the interfacial film on the surfaces of the positive electrode and the negative electrode is further improved, the formed interfacial film has excellent thermal stability and electrochemical stability, and the side reaction of the electrolyte can be obviously inhibited in a high-voltage system, so that the high-temperature cycle and normal-temperature cycle performance of the lithium ion battery can be obviously improved.
In some embodiments, the weight percent of the carbonate additive is 0.1 wt% to 20 wt% based on the weight of the electrolyte. In some embodiments, the weight percent of the carbonate additive is about 0.1 wt%, about 0.5 wt%, about 1 wt%, about 2 wt%, about 3 wt%, about 4 wt%, about 5 wt%, about 6 wt%, about 7 wt%, about 8 wt%, about 9 wt%, about 10 wt%, about 11 wt%, about 12 wt%, about 13 wt%, about 14 wt%, about 15 wt%, about 16 wt%, about 17 wt%, about 18 wt%, about 19 wt%, about 20 wt%, 0.1 wt% to 5 wt%, 1 wt% to 5 wt%, 5 wt% to 10 wt%, 1 wt% to 10 wt%, 5 wt% to 15 wt%, or 10 wt% to 20 wt%, etc., based on the weight of the electrolyte.
Other additives
In some embodiments, the electrolyte of the present application may further comprise vinylene carbonate. The weight percentage of vinylene carbonate is 0.01 wt% to 4 wt%, based on the weight of the electrolyte. When the weight percentage of the vinylene carbonate is less than 0.01 wt%, the vinylene carbonate has less influence on the formation of a Solid Electrolyte Interface (SEI) film on the surface of the negative electrode and has less effect on the improvement of the cycle performance of the electrochemical device; when the weight percentage of vinylene carbonate is higher than 4 wt%, the storage gassing property of the electrochemical device is deteriorated, and the electrochemical device is caused to be charged and separated from lithium at a low temperature.
In some embodiments, the electrolytes of the present application can also include 1, 3-propane sultone. The weight percentage of 1, 3-propane sultone is 0.1 wt% to 5 wt% based on the weight of the electrolyte. When the weight percentage of 1, 3-propane sultone is less than 0.1 wt%, it has less influence on the formation of an SEI film on the surface of the positive electrode, and the improvement on high-temperature storage of an electrochemical device is weak; when the weight percentage of 1, 3-propane sultone is more than 5 wt%, low-temperature discharge performance of the electrochemical device may be deteriorated, increasing manufacturing costs.
In some embodiments, the electrolyte of the present application may further comprise lithium difluorooxalato borate. The weight percent of lithium difluorooxalato borate is 0.01 wt% to 2 wt% based on the weight of the electrolyte. When the weight percentage of the lithium difluoro (oxalato) borate is lower than 0.1 wt%, the lithium difluoro (oxalato) borate is insufficient in film formation on the surface of a negative electrode, and the effect of improving the cycle performance of an electrochemical device is weak; when the weight percentage of lithium difluorooxalato borate is more than 2 wt%, the negative electrode film formation is too thick, and the low-temperature charging performance is deteriorated.
In some embodiments, the electrolyte of the present application further includes an organic solvent, and a specific kind of the organic solvent is not limited, and in particular, in some embodiments, the organic solvent includes at least one of dimethyl carbonate, methyl ethyl carbonate, methyl propyl carbonate, methyl isopropyl carbonate, methyl butyl carbonate, diethyl carbonate, dipropyl carbonate, dibutyl carbonate, ethylene carbonate, propylene carbonate, butylene carbonate, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, methyl propionate, ethyl propionate, propyl propionate, butyl propionate, methyl butyrate, ethyl butyrate, propyl butyrate, methyl valerate, ethyl valerate, methyl pivalate, ethyl pivalate, butyl pivalate, γ -butyrolactone, or γ -valerolactone.
In some embodiments, the electrolyte of the present application further comprises a lithium salt selected from at least one of inorganic lithium salts and organic lithium salts. In some embodiments, the lithium salt is selected from lithium hexafluorophosphate (LiPF)6) Lithium tetrafluoroborate (LiBF)4) Lithium hexafluoroarsenate, lithium perchlorate, lithium bis (fluorosulfonylimide) (LiFSI), lithium bis (trifluoromethanesulfonylimide) (LiTFSI), or lithium bis (oxalato) borate (LiBOB). In some embodiments, the lithium salt is selected from lithium hexafluorophosphate.
In some embodiments, the concentration of the lithium salt in the electrolyte is 0.6mol/L to 2 mol/L. In some embodiments, the concentration of the lithium salt in the electrolyte is about 0.6mol/L, about 0.8mol/L, about 1mol/L, about 1.2mol/L, about 1.4mol/L, about 1.6mol/L, about 1.8mol/L, about 2mol/L, 0.6mol/L to 1.2mol/L, 0.8mol/L to 1.2mol/L, 1mol/L to 1.6mol/L, or 1mol/L to 2mol/L, and the like.
Two, electrochemical device
Embodiments of the present application also provide an electrochemical device comprising a positive electrode, a negative electrode, a separator, and an electrolyte of the present application. The electrochemical device of the present application may include any device in which electrochemical reactions occur, and specific examples thereof include all kinds of primary batteries, secondary batteries, fuel cells, solar cells, or capacitors. In particular, the electrochemical device is a lithium secondary battery including a lithium metal secondary battery, a lithium ion secondary battery, a lithium polymer secondary battery, or a lithium ion polymer secondary battery. In some embodiments, the electrochemical device of the present application includes a positive electrode having a positive electrode active material capable of occluding and releasing metal ions; a negative electrode having a negative electrode active material capable of occluding and releasing metal ions; a separator interposed between the positive electrode and the negative electrode; and an electrolyte of the present application. In some embodiments, the electrochemical device may be a pouch cell, a cylindrical cell, or a prismatic cell.
Electrolyte solution
The electrolyte used in the electrochemical device of the present application is any of the electrolytes described above in the present application. In addition, the electrolyte used in the electrochemical device of the present application may further include other electrolytes within a range not departing from the gist of the present application.
Positive electrode
The positive electrode of the present application includes a positive current collector and a positive active material layer disposed on the positive current collector. The positive electrode active material in the positive electrode active material layer includes a compound that reversibly intercalates and deintercalates lithium ions. The positive electrode active material may include a composite oxide containing lithium and at least one element selected from cobalt, manganese, and nickel. The specific kind of the positive electrode active material is not particularly limited and may be selected as desired. In some embodiments, the positive active material is selected from lithium cobaltate (LiCoO)2) Lithium nickel manganese cobalt ternary material and lithium manganate (LiMn)2O4) Lithium nickel manganese oxide (LiNi)0.5Mn1.5O4) Or lithium iron phosphate (LiFePO)4) At least one of (1).
In some embodiments, the positive electrode active material may have a coating layer on the surface, or may be mixed with another compound having a coating layer. The coating may include at least one coating element compound selected from an oxide of the coating element, a hydroxide of the coating element, an oxyhydroxide of the coating element, an oxycarbonate (oxycarbonate) of the coating element, and an oxycarbonate (hydroxycarbonate) of the coating element. The compounds used for the coating may be amorphous or crystalline.
In some embodiments, the coating elements contained in the coating may include Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Zr, or mixtures thereof. The coating layer may be applied by any method as long as the method does not adversely affect the properties of the positive electrode active material. For example, the method may include any coating method well known to those of ordinary skill in the art, such as spraying, dipping, and the like.
In some embodiments, the positive active material layer further includes a binder. The binder may improve the binding of the positive electrode active material particles to each other and also improve the binding of the positive electrode active material to the positive electrode current collector. In some embodiments, the binder may include, but is not limited to, polyvinyl alcohol, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide containing polymers, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene 1, 1-difluoride, polyethylene, polypropylene, styrene butadiene rubber, acrylated styrene butadiene rubber, epoxy, nylon, and the like.
In some embodiments, the positive active material layer further includes a conductive material, thereby imparting conductivity to the electrode. The conductive material may include any conductive material as long as it does not cause a chemical change. In some embodiments, the conductive material may include, but is not limited to, carbon-based materials (e.g., natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, carbon fiber, etc.), metal-based materials (e.g., metal powders, metal fibers, etc., including, for example, copper, nickel, aluminum, silver, etc.), conductive polymers (e.g., polyphenylene derivatives), and mixtures thereof.
In some embodiments, the positive current collector may be, but is not limited to, aluminum.
The positive electrode may be prepared by a preparation method well known in the art. For example, the positive electrode can be obtained by: the active material, the conductive material, and the binder are mixed in a solvent to prepare an active material composition, and the active material composition is coated on a current collector. In some embodiments, the solvent may include, but is not limited to, N-methylpyrrolidone, and the like.
In some embodiments, the positive electrode is made by forming a positive electrode material on a current collector using a positive electrode active material layer including a lithium transition metal-based compound powder and a binder.
In some embodiments, the positive active material layer may be generally fabricated by: the positive electrode active material and a binder (a conductive material, a thickener, and the like, which are used as needed) are dry-mixed to form a sheet, and the obtained sheet is pressure-bonded to a positive electrode current collector, or these materials are dissolved or dispersed in a liquid medium to form a slurry, which is applied to the positive electrode current collector and dried. In some embodiments, the material of the positive electrode active material layer includes any material known in the art.
Negative electrode
The negative pole of this application includes that the negative pole mass flow body and the negative pole active material layer of setting on the negative pole mass flow body, and the specific kind of the negative pole active material in the negative pole active material layer does not all receive specific restriction, can select according to the demand. In some embodiments, the negative active material is selected from natural graphite, artificial graphite, mesophase micro carbon spheres (abbreviated as MCMB), hard carbon, soft carbon, silicon-carbon composite, Li-Sn alloy, Li-Sn-O alloy, Sn, SnO2Spinel-structured lithiated TiO2-Li4Ti5O12Or a Li-Al alloy. Non-limiting examples of carbon materials include crystalline carbon, amorphous carbon, and mixtures thereof. The crystalline carbon may be natural graphite or artificial graphite in an amorphous form or in a form of a flake, a platelet, a sphere or a fiber. The amorphous carbon may be soft carbon, hard carbon, mesophase pitch carbide, calcined coke, or the like.
In some embodiments, the negative active material layer may include a binder that improves the binding of the negative active material particles to each other and to the negative current collector. Non-limiting examples of binders include polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide containing polymers, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene 1, 1-difluoroethylene, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy, nylon, and the like.
In some embodiments, the negative active material layer includes a conductive material, thereby imparting conductivity to the electrode. The conductive material may include any conductive material as long as it does not cause a chemical change. Non-limiting examples of the conductive material include carbon-based materials (e.g., natural graphite, ink, carbon black, acetylene black, ketjen black, carbon fiber, etc.), metal-based materials (e.g., metal powder, metal fiber, etc., such as copper, nickel, aluminum, silver, etc.), conductive polymers (e.g., polyphenylene derivatives), and mixtures thereof.
In some embodiments, the Dv50 of the anode active material particles is 10 μm to 18 μm. When the Dv50 of the anode active material particles is less than 10 μm, it may cause an acceleration in cycle decay of the electrochemical device; when the Dv50 of the anode active material particles is greater than 18 μm, the anode of the electrochemical device swells seriously during the cycle, accelerating the consumption of the electrolyte, resulting in accelerated cycle degradation of the electrochemical device. In some embodiments, the Dv50 of the negative active material particles is about 10 μm, about 11 μm, about 12 μm, about 13 μm, about 14 μm, about 15 μm, about 16 μm, about 17 μm, about 18 μm, 11 μm to 14 μm, 11 μm to 16 μm, or 14 μm to 18 μm.
In some embodiments, the negative current collector may be selected from the group consisting of copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, polymer substrates coated with conductive metals, and combinations thereof.
Isolation film
In some embodiments, the electrochemical device of the present application is provided with a separator between the positive electrode and the negative electrode to prevent short circuit. The material and shape of the separation film used in the electrochemical device of the present application are not particularly limited, and may be any of the techniques disclosed in the prior art. In some embodiments, the separator includes a polymer or inorganic substance or the like formed of a material stable to the electrolyte of the present application.
In some embodiments, the release film may include a substrate layer and a surface treatment layer. The substrate layer is a non-woven fabric, a film or a composite film with a porous structure, and the material of the substrate layer is at least one selected from polyethylene, polypropylene, polyethylene terephthalate and polyimide. Specifically, a polypropylene porous film, a polyethylene porous film, a polypropylene nonwoven fabric, a polyethylene nonwoven fabric, or a polypropylene-polyethylene-polypropylene porous composite film can be used.
In some embodiments, a surface treatment layer is disposed on at least one surface of the substrate layer, and the surface treatment layer may be a polymer layer or an inorganic layer, or a layer formed by mixing a polymer and an inorganic substance.
In some embodiments, the inorganic layer includes inorganic particles selected from one or a combination of alumina, silica, magnesia, titania, hafnia, tin oxide, ceria, nickel oxide, zinc oxide, calcium oxide, zirconia, yttria, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, and barium sulfate, and a binder. The binder is selected from one or a combination of more of polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene and polyhexafluoropropylene.
In some embodiments, the polymer layer comprises a polymer selected from at least one of polyamide, polyacrylonitrile, acrylate polymer, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinyl ether, polyvinylidene fluoride, and poly (vinylidene fluoride-hexafluoropropylene).
Electronic device
The electrochemical device of the present application has excellent high-temperature cycle properties and high-low temperature storage properties, so that the electrochemical device manufactured thereby is suitable for electronic devices in various fields.
The use of the electrochemical device of the present application is not particularly limited, and it may be used for any use known in the art. In one embodiment, the electrochemical device of the present application can be used in, but is not limited to, notebook computers, pen-input computers, mobile computers, electronic book players, cellular phones, portable facsimile machines, portable copiers, portable printers, headphones, video recorders, liquid crystal televisions, portable cleaners, portable CDs, mini-discs, transceivers, electronic organizers, calculators, memory cards, portable recorders, radios, backup power supplies, motors, automobiles, motorcycles, mopeds, bicycles, lighting fixtures, toys, game machines, clocks, power tools, flashlights, cameras, household large batteries, lithium ion capacitors, and the like.
Fourth, example
The following describes performance evaluation according to examples and comparative examples of lithium ion batteries of the present application. It should be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the present application.
Preparation of lithium ion battery
(1) Preparation of the Positive electrode
Mixing lithium cobaltate, conductive carbon black and vinylidene fluoride according to the weight ratio of 97:1.4:1.6, adding N-methyl pyrrolidone, and uniformly stirring under the action of a vacuum stirrer to obtain anode slurry; uniformly coating the positive electrode slurry on a positive electrode current collector aluminum foil; drying the aluminum foil at 85 ℃, then carrying out cold pressing to obtain a positive active material layer, then carrying out cutting and slitting, and drying for 4h under the vacuum condition of 85 ℃ to obtain the positive electrode.
(2) Preparation of the negative electrode
Mixing artificial graphite, sodium carboxymethylcellulose and styrene butadiene rubber according to the weight ratio of 97.9:0.5:1.6, adding deionized water, and obtaining cathode slurry under the action of a vacuum stirrer; uniformly coating the negative electrode slurry on a copper foil of a negative electrode current collector; and drying the copper foil at 85 ℃, then carrying out cold pressing to obtain a negative electrode active material layer, then carrying out cutting and slitting, and drying for 12h under the vacuum condition of 120 ℃ to obtain the negative electrode.
(3) Preparation of the electrolyte
Mixing Ethylene Carbonate (EC), Ethyl Methyl Carbonate (EMC) and diethyl carbonate (DEC) in a dry argon atmosphere glove box according to the mass ratio of EC to EMC to DEC to 30:50:20, adding an additive, dissolving and fully stirring, and adding lithium salt LiPF6And mixing uniformly to obtain the electrolyte. Wherein, LiPF6The concentration of (2) is 1 mol/L. Specific structural formulas and contents of the additives used in the electrolyte are shown in tables 1,3, 5 and 7. In each table, the content of the additive is a weight percentage calculated based on the total weight of the electrolyte.
(4) Preparation of the separator
A polyethylene barrier film with a thickness of 7 μm was used.
(5) Preparation of lithium ion battery
And sequentially stacking the anode, the isolating film and the cathode to enable the isolating film to be positioned between the anode and the cathode to play an isolating role, then winding, welding a tab, placing the tab into an outer packaging foil aluminum plastic film, injecting the prepared electrolyte, and carrying out vacuum packaging, standing, formation, shaping, capacity test and other processes to obtain the soft package lithium ion battery (the thickness is 3.3mm, the width is 39mm, and the length is 96 mm).
The lithium ion batteries of the examples and comparative examples of the present application were prepared according to the above-described method.
Test method
(1) High temperature storage Performance test
Discharging the lithium ion battery to 3.0V at 25 ℃ at 0.5C, charging to 4.45V at 0.7C, charging to 0.05C at constant voltage at 4.45V, testing with a micrometer, and recording the thickness of the lithium ion battery as H11Placing the lithium ion battery in a 60 ℃ oven for 30 days, testing and recording the thickness of the lithium ion battery by using a micrometer after the test is finished, and recording the thickness as H12。
Thickness expansion ratio ═ H12-H11)/H11×100％。
(2) DC impedance DCR (25 ℃ C.) test
The lithium ion battery is tested according to the following steps:
1) standing for 4h in a high-low temperature box at 25 ℃;
2) charging to 4.45V at constant current of 0.7C, charging to 0.05C at constant voltage, and standing for 10 min;
3) discharging to 3.4V at constant current of 0.1C, and standing for 5min (to obtain actual capacity);
4) standing for 5min, charging to 4.45V at constant current of 0.7C, and charging to 0.05C at constant voltage (calculated by actual capacity obtained in step 3);
5) standing for 10 min;
6) constant current discharge at 0.1C for 8h (calculated from the actual capacity obtained in step 3), and recording the voltage at this time as V1；
7)1C constant current discharge for 1s (the capacity is calculated by the labeled capacity of the lithium ion battery), and the voltage at the moment is recorded as V2；
8) Calculating the direct current impedance corresponding to the lithium ion battery 20% SOC state, wherein the 20% SOC direct current impedance is (V)1-V2) and/1C (capacity is calculated by marking the capacity of the lithium ion battery).
(3) High temperature cycle performance test
Respectively placing the lithium ion batteries subjected to the high-temperature cycle performance test in a 45 ℃ high-temperature box and carrying out the following test steps;
1) charging to 4.45V at constant current of 0.7C and charging to 0.05C at constant pressure, and standing for 10 s;
2) discharging at constant current of 1C to 3.2V, standing for 5min (this is the first cycle, recording the discharge capacity C of the first cycle0)；
3) Repeat step 1 and step 2 for 1000 cycles and record the discharge capacity C after 1000 cycles1. And respectively calculating the capacity retention rate of the lithium ion battery after 1000 cycles. The capacity retention after cycling was calculated as follows: capacity retention after cycling ═ C1/C0)×100％。
(4) Low temperature cycle performance test
Respectively placing the lithium ion batteries subjected to the low-temperature cycle performance test in a high-temperature box at 12 ℃ and carrying out the following test steps;
1) charging to 4.45V at constant current of 0.7C and charging to 0.05C at constant pressure, and standing for 10 s;
2) discharging at constant current of 1C to 3.2V, standing for 5min (this is the first cycle)Ring, recording first cycle discharge capacity C0)；
3) Repeat step 1 and step 2 for 1000 cycles and record the discharge capacity C after 1000 cycles1. And respectively calculating the capacity retention rate of the lithium ion battery after 1000 cycles. The capacity retention after cycling was calculated as follows: capacity retention after cycling ═ C1/C0)×100％。
(5) Low temperature discharge test
The lithium ion battery is tested according to the following steps:
1) standing for 1h in a high-low temperature box at 25 ℃;
2) charging to 4.45V at constant current of 0.7C, charging to 0.05C at constant voltage, and standing for 10 min;
3) discharging at constant current of 0.2C to 3.0V, standing for 5min (discharge capacity C)2)；
4) Standing at-20 deg.C for 30min, constant-current charging to 4.45V at 0.7C, constant-voltage charging to 0.05C, and standing for 10 min;
5) discharging at constant current of 0.2C to 3.0V, standing for 5min (discharge capacity C)3)；
6) Calculating the low-temperature discharge capacity retention rate, the low-temperature discharge capacity retention rate ═ C3/C2×100％。
Test results
Table 1 shows electrolyte parameters of examples 1 to 27 and comparative examples 1 to 6, and table 2 shows electrical property test results of the lithium ion batteries of examples 1 to 27 and comparative examples 1 to 6. The graphite particles Dv50 of examples 1 to 27 and comparative examples 1 to 6 were each 14 μm.
TABLE 1
Figure BDA0002555335640000201
Figure BDA0002555335640000211
TABLE 2
Figure BDA0002555335640000212
Figure BDA0002555335640000221
As can be seen from tables 1 and 2, the addition of the thiane compound and the polynitrile compound to the electrolyte effectively improves the high-temperature cycle performance and the low-temperature discharge performance of the lithium ion battery and effectively reduces the dc resistance by the synergistic effect of the thiane compound and the polynitrile compound.
Table 3 shows electrolyte parameters of examples 28 to 38 and comparative examples 1 and 7 to 10, and table 4 shows electrical property test results of the lithium ion batteries of examples 28 to 38 and comparative examples 1 and 7 to 10. The graphite particles Dv50 of examples 28 to 38 and comparative examples 1 to 10 were all 14 μm.
TABLE 3
Figure BDA0002555335640000222
TABLE 4
Figure BDA0002555335640000231
As can be seen from tables 3 and 4, the cyclic sulfate compound can significantly suppress deformation of the lithium ion battery under high-temperature long-term storage conditions, and also has an effect of improving the high-temperature cycle performance of the lithium ion battery. The thiane compound, the polynitrile compound and the cyclic sulfate compound are added into the electrolyte, so that the cycle performance and the high-temperature storage performance of the lithium ion battery can be effectively improved. The cyclic sulfate compound and the thiane compound can cooperate to form an SEI film on a negative electrode, and the polynitrile compound can form a film on a positive electrode to stabilize the positive electrode, so that the cycle performance and the high-temperature long-term storage performance of the lithium ion battery can be effectively improved.
Table 5 shows electrolyte parameters of examples 39 to 57 and comparative examples 1 and 11 to 14, and table 6 shows electrical property test results of the lithium ion batteries of examples 39 to 57 and comparative examples 1 and 11 to 14.
The graphite particles Dv50 of examples 39 to 57 and comparative examples 1 to 14 were all 14 μm.
TABLE 5
Figure BDA0002555335640000232
Figure BDA0002555335640000241
TABLE 6
Figure BDA0002555335640000242
Figure BDA0002555335640000251
As can be seen from tables 5 and 6, the addition of the carbonate compound to the electrolyte solution can further improve the cycle performance of the lithium ion battery. When the content of the carbonate compound is more than 20 wt%, the interface kinetics of the negative electrode may be deteriorated, and the improvement effect on the cycle performance of the lithium ion battery may be reduced. The interfacial film formed by the carbonate compound has better mechanical stability, can form an ion channel with the cooperation of the cyclic sulfate compound and the thiane compound, and the carbonate compound has larger dielectric constant, so that the dynamics of the electrolyte can be improved; the polynitrile compound can form a film on the anode to stabilize the anode, and the four synergistic effects can effectively improve the high-low temperature cycle performance and the high-temperature long-term storage performance of the lithium ion battery.
Table 7 shows anode active materials and electrolyte parameters of example 8, examples 58 to 71, and comparative examples 1 to 3, and table 8 shows electrical property test results of the lithium ion batteries of example 8, examples 58 to 71, and comparative examples 1 to 3.
TABLE 7
Figure BDA0002555335640000252
Figure BDA0002555335640000261
TABLE 8
Figure BDA0002555335640000262
As can be seen from comparison of examples 58 to 71 with comparative examples 1 to 3, when the graphite particles Dv50 are less than 10 μm, the coulombic efficiency of the lithium ion battery is severely deteriorated, resulting in accelerated cycle decay of the lithium ion battery; when the Dv50 of the graphite particles is larger than 18 μm, the negative electrode of the lithium ion battery swells seriously during the cycle, which accelerates the consumption of the electrolyte, resulting in accelerated cycle degradation of the lithium ion battery.
Reference throughout this specification to "some embodiments," "one embodiment," "another example," "an example," "a specific example," or "some examples" means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present application. Thus, throughout the specification, descriptions appear, for example: "in some embodiments," "in an embodiment," "in one embodiment," "in another example," "in one example," "in a particular example," or "by example," which do not necessarily refer to the same embodiment or example in this application. Furthermore, the particular features, structures, materials, or characteristics may be combined in any suitable manner in one or more embodiments or examples.
Although illustrative embodiments have been illustrated and described, it will be appreciated by those skilled in the art that the above embodiments are not to be construed as limiting the application and that changes, substitutions and alterations can be made to the embodiments without departing from the spirit, principles and scope of the application.

Claims (13)

1. An electrolyte comprising a thiane compound and a polynitrile compound represented by formula I
Figure FDA0002555335630000011
Wherein R is1、R2、R3、R4Each independently selected from substituted or unsubstituted C1To C6Alkylene or sulfonyl, wherein, when substituted, the substituent is cyano, sulfonylmethyl, C1To C6At least one of an alkoxy group or a fluorine atom.
2. The electrolyte of claim 1, wherein the thiane compound comprises:
Figure FDA0002555335630000012
Figure FDA0002555335630000013
at least one of (1).
3. The electrolyte of claim 1, wherein the weight percent of the thiane compound is 0.05 to 10 weight percent and the weight percent of the polynitrile compound is 0.1 to 10 weight percent, based on the weight of the electrolyte.
4. The electrolyte of claim 1, wherein the polynitrile compound comprises a compound of formula II
Figure FDA0002555335630000014
Wherein R is6Is cyano, fluorine atom, hydrogen atom, substituted or unsubstituted C1To C6Alkyl or substituted or unsubstituted C1To C6Alkoxy, wherein when substituted, the substituent is at least one of cyano, fluorine atom or sulfone group;
wherein R is5、R7Each independently selected from substituted or unsubstituted C1To C6Alkylene or substituted or unsubstituted C1To C6And an alkyleneoxy group, wherein when substituted, the substituent is at least one of a cyano group, a fluorine atom, or a sulfone group.
5. The electrolyte of claim 1, wherein the polynitrile compound comprises:
Figure FDA0002555335630000021
Figure FDA0002555335630000022
at least one of (1).
6. The electrolyte of claim 1, wherein the electrolyte further comprises a cyclic sulfate compound represented by formula III
Figure FDA0002555335630000023
Wherein R is9、R11Each independently selected from substituted or unsubstituted C1To C6Alkylidene, wherein when substituted, the substituent is cyano, sulfonylmethyl, fluorosulfonyl, C1To C6At least one of an alkoxy group or a fluorine atom;
wherein R is10Selected from oxygen atoms, substituted or unsubstituted C1To C6Alkylene, wherein, when substituted, the substituents are cyano, sulfonylmethyl, fluorosulfonyl, C1To C6At least one of an alkoxy group or a fluorine atom;
wherein R is8、R12Each independently selected from a hydrogen atom, a fluorine atom, a substituted or unsubstituted C1To C6Alkyl, wherein when substituted, the substituent is sulfonylmethyl, fluorosulfonyl or C1To C6At least one of an alkoxy group, a fluorine atom, or a cyano group;
wherein the weight percentage of the cyclic sulfate compound is 0.1 to 10 wt% based on the weight of the electrolyte.
7. The electrolyte of claim 6, wherein the cyclic sulfate compound comprises:
Figure FDA0002555335630000031
at least one of (1).
8. The electrolyte of claim 1, wherein the electrolyte further comprises a carbonate additive comprising at least one of a compound of formula IV-a, a compound of formula IV-B, or a compound of formula IV-C:
Figure FDA0002555335630000033
wherein R is13、R14Each independently selected from a hydrogen atom, a fluorine atom, a cyano group, a substituted or unsubstituted C1To C6Alkyl, substituted or unsubstituted C2To C6Alkenyl, substituted or unsubstituted C2To C6Alkynyl, substituted or unsubstituted C6To C10Aryl or substituted or unsubstituted-Rb-O-RaWherein R isaIs cyano or C1To C3Alkyl radical, RbIs a single bond or C1To C3Wherein when substituted, the substituent is at least one of a cyano group, a sulfone group or a fluorine atom;
wherein R is15、R16、R17、R18Each independently selected from a hydrogen atom, a fluorine atom, a cyano group, a substituted or unsubstituted C1To C6Alkyl, substituted or unsubstituted C2To C6Alkenyl, substituted or unsubstituted C2To C6Alkynyl, substituted or unsubstituted C6To C10Aryl or substituted or unsubstituted C1To C6Alkoxy, wherein when substituted, the substituent is at least one of cyano, sulfone or fluorine atom;
wherein R is13、R14Not being hydrogen atoms at the same time; and is
Wherein R is17、R18At least one of which is substituted with a fluorine atom.
9. The electrolyte of claim 8, wherein the weight percentage of the carbonate additive is 0.1 wt% to 20 wt% based on the weight of the electrolyte.
10. The electrolyte of claim 8, wherein the carbonate additive comprises:
Figure FDA0002555335630000041
at least one of (1).
11. An electrochemical device comprising a positive electrode, a negative electrode, a separator and the electrolyte of any one of claims 1-10.
12. The electrochemical device according to claim 11, wherein the negative electrode includes a negative electrode active material, the negative electrode active material particles having a Dv50 of 10 μm to 18 μm.
13. An electronic device comprising the electrochemical device of any one of claims 11 to 12.
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